Why you can't trust 3D scans of cities

Without its correction algorithms, the canner had trouble with air particles, clouds and glass

ScanLAB

How Oberbaum Bridge should look

Alamy

This article was taken from the June 2014 issue
of Wired magazine. Be the first to read Wired's articles in print
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3D scanners are now used for
everything from inspecting the integrity of bridges to predicting
flood risks. But with so much riding on the accuracy of these
results, what happens if the machine makes a mistake? That's the
question troubling Matthew Shaw, cofounder of London-based ScanLAB: "Now that the
technology is becoming affordable, there are many non-expert users
who aren't questioning what it does, they're just accepting the
results," he says. So Shaw and his cofounder William Trossell set
out to show them just what a 3D scan would look like if its
correction algorithms tripped.

The pair hacked their scanner to
disable its normal filtering software, then scanned Tempelhof
Airport and Oberbaum Bridge (pictured) in Berlin. The machine they
used fired up to 976,000 laser pulses a second, calculating the
shape and distance of surrounding objects based on the time the
light takes to reflect back. By rotating this laser and placing a
point at every distance recorded, it built up a near
millimetre-precise 3D picture of its surroundings -- but without
any corrections, the results are nothing like the images a typical
user would expect.

With companies such as Google
experimenting with the technology to try and document cities,
ScanLAB's project is a lesson for planners. Glass buildings are
common, but as Shaw points out, "if you raw-scan a city in the
future, you won't be able to see them. If it's made of glass, it's
just not there."